This invention relates generally to biocidal compositions and methods for using these compositions. In particular, this invention relates to long-acting biocidal compositions which may remain effective for weeks, months or even years.
The use of various disinfecting and sterilizing compounds to disinfect surfaces is known in the art. Chlorine compounds have been used for this purpose. Chlorine dioxide, in particular, has been found to be an especially effective germ killer. This compound is quite versatile and has been used as a bleaching agent such as in the oxidation of the natural colorant present in cotton, wood pulp, and other cellulosic fibrous materials. In these uses, the chlorine dioxide oxidizes the treated material yet is noninjurious to the fibrous materials.
Chlorine dioxide has also been used in the treatment of water supplies. It is commercially available in powder form for use in swimming pools, and in liquid form for use in household and industrial cleaning and disinfecting.
Chlorine dioxide is generally considered to be at least as effective as, if not superior to, chlorine gas as a bactericide, sporicide or virucide. Moreover, chlorine dioxide retains its germ-killing capacity to a significantly greater extent over a wider pH range than does gaseous chlorine.
Due to its explosive nature in concentrated form, chlorine dioxide gas is not generally used directly as a chemical reagent. It has instead become the general practice to use a chlorine dioxide-liberating compound such as sodium chlorite as the source of the chlorine dioxide gas.
Sodium chlorite has been found to form a particularly effective germ-killing composition when combined with lactic acid. U.S. Pat. No. 4,084,747 discloses germ-killing compositions and methods which employ sodium chlorite and lactic acid in aqueous solution. U.S. Pat. No. 4,330,531 discloses various germ-killing materials such as gels, toothpastes and soaps which are prepared using sodium chlorite and lactic acid as the active germ-killing ingredients.
Although prior art uses of compositions which employ a chlorine dioxide-liberating compound and a weak organic acid, such as lactic acid, have been successful as disinfectants, the germ-killing action has not been maintained for very long beyond the time of application. For this reason, surfaces which have been successfully disinfected may be susceptible to recontamination within a fairly short time.
The reaction of a chlorine dioxide-liberating compound, such as sodium chlorite, and lactic acid is completed within a relatively short period of time and the chlorine dioxide diffuses after it is released. Accordingly, the chlorine dioxide dissipates rather quickly from the microenvironment which exists immediately above the treated surface. This leaves the recently treated surface unprotected against recontamination.
The search has continued for long-acting disinfectant and biocidal compositions, and methods of making and using such compositions. This invention was made as a result of that search.